A conventional EPROM with an identification code includes an internal circuit operating as a EPROM, a code setting circuit storing predetermined identification code, a switching circuit which is composed of plural logic gates and is connected at inputs to the internal circuit and the code setting circuit, and a control circuit for controlling the switching circuit to selectively supply one of outputs of the internal circuit and the code setting circuit to an output circuit.
In this conventional EPROM with an identification code, when a mode in which information stored in the internal circuit is read out is instructed by a selection signal of the control circuit, a signal from the internal circuit to the output circuit, and an identification code is not read from the code setting circuit. On the other hand, when a mode in which a predetermined identification code is read out is instructed, a signal from the code setting circuit is transferred through the switching circuit by disconnecting a signal line of the internal circuit.
According to the conventional EPROM with an identification code, however, there are disadvantages in that the switching circuit becomes complicated in structure and large in an occupying area, when the bit number of an identification code and/or functions of an EPROM are increased, because the switching circuit operates in accordance with levels of signals supplied from the control circuit and the code setting circuit. For this reason, the number of transistors which are arranged longitudinally in the switching circuit is increased. As a result, the transfer speed of a signal read from the internal circuit is lowered.